A DPF (Diesel Particulate Filter), etc. is installed for trapping particular matter (PM) composed predominantly of soot contained in exhaust gas from automobiles, etc., and as a PM detection sensor for detecting failure of the DPF, etc., for example, as described in Patent Literature 1, there is disclosed a particulate matter detecting device comprising an insulating substrate formed of a ceramic sintered body such as an aluminum oxide sintered body, a sensing electrode formed on a surface of the insulating substrate by a thick-film printing technique (screen printing method), and so forth. This device detects particulate matter based on variation in electrical characteristics resulting from accumulation of detection targets, such as PM, contained in exhaust gas in between a pair of sensing electrodes.
Meanwhile, for example, as described in Patent Literature 2, there is disclosed a method of manufacturing a PM detection sensor having a pair of electrodes, the method of forming a pair of sensing electrodes, etc. by other technique than the thick-film printing technique (more specifically, the method comprising forming a laminate structure by laminating sensing electrodes, etc. one after another in a width direction thereof, and slicing the laminate structure in a predetermined thickness by means of dicing saw or otherwise).
Moreover, for example, as described in Patent Literature 3 or Patent Literature 4, as a sensor substrate which is used for an exhaust gas sensor or the like, there is used a sensor substrate comprising an insulating substrate formed of a ceramic sintered body such as an aluminum oxide sintered body, and a pair of sensing electrodes disposed on a surface of the insulating substrate.
For example, on the basis of variation in resistance value or current value caused by accumulation of detection targets contained in exhaust gas in between a pair of the sensing electrodes, the content, etc. of the detection targets in the exhaust gas can be detected.
The capability of detecting detection targets contained in exhaust gas with high accuracy is demanded in the above-described sensor substrate and sensor device.